Method and apparatus for hysteresis control

ABSTRACT

A hysteresis control method for a control system includes setting an arbitrary reference value for an existing position of a control width and calculating a difference between a present input value and the arbitrary reference value. A direction of increase/decrease from a control value and an input value variation width are calculated. A control value is calculated for the present input value time from the calculated input value variation width and the calculated direction of increase/decrease.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for hysteresiscontrol.

2. Description of the Related Art

As an example of a hysteresis control apparatus, one disclosed in theUnexamined Japanese Patent Publication No. 8-115068 (see paragraphnumbers 0009 to 0020, FIG. 1 to FIG. 3) is known. An overview of thehysteresis control apparatus will be explained with reference to FIG. 1below. FIG. 1 is a block diagram showing an example of the configurationof a conventional hysteresis control apparatus.

The hysteresis control apparatus shown in FIG. 1 is provided with afirst signal comparator 801 that compares a relationship in magnitudebetween an input signal value and set value (input signal value>setvalue), a second signal comparator 802 that compares a relationship inmagnitude between an input signal value and set value (input signalvalue<set value), a control circuit 803 that processes the comparisonresults at the first signal comparator 801 and second signal comparator802 and a signal switching circuit 804 that outputs the output value ofthe control circuit 803 with a hysteresis characteristic added thereto.

It should be noted here that, for example, in a mobile communicationsystem, transmit power control is performed to solve a near-far problem.This transmit power control involves a plurality of control sections,each of which constitutes an input value operating variation width. FIG.2 is a time chart illustrating a control mode which is assumed whenhysteresis control is performed using the hysteresis control apparatusshown in FIG. 1 in such a control system having a plurality of controlsections.

FIG. 2 shows four control sections a, b, c and d. The control section ais an input value operating variation width including a hysteresiscontrol section A. The control section b is an input value operatingvariation width including hysteresis control sections A and B. Thecontrol section c is an input value operating variation width includinghysteresis control sections B and C. The control section d is an inputvalue operating variation width including the hysteresis control sectionC.

In the hysteresis control section A, a comparison is made at a maximumvalue in the control section a and a minimum value in the controlsection b to decide whether or not to make a transition to theneighboring control section. In the hysteresis control section B, acomparison is made at a maximum value in the control section b and aminimum value in the control section c to decide whether or not to makea transition to the neighboring control section. In the hysteresiscontrol section C, a comparison is made at a maximum value in thecontrol section c and a minimum value in the control section d to decidewhether or not to make a transition to the neighboring control section.

However, according to the hysteresis control method using the abovedescribed conventional hysteresis control apparatus, it is necessary toperform two comparisons in the hysteresis control sections and changethe set values until control values (output values) in the controlsections to which a transition is to be made are obtained. Furthermore,there is a problem that in order to know a variation in a controlsection, it is not possible to detect an input value variation widthextending over the control sections unless a difference from theimmediately preceding control section is calculated after a desiredcontrol value is determined.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method andapparatus for hysteresis control, when there is a plurality of controlsections, each of which constitutes an input value operating variationwidth having hysteresis control sections at both ends, requiring onlyone comparison in each hysteresis control section, capable ofcalculating control values without the need to change set values anddetecting an input value variation width extending over the controlsections while performing hysteresis control.

According to an aspect of the present invention, a hysteresis controlmethod in a control system having a plurality of control sections whichare input value operating variation widths having hysteresis controlsections at both ends comprises the steps of setting an arbitraryreference value which serves as a reference for deciding an existingposition of a control width in the control section, calculating adifference between an input value this time and the arbitrary referencevalue in the control section to which a preceding input value belongs,generating position information indicating a positional relationshipbetween the input value this time and the arbitrary reference value inthe control section to which the preceding input value belongs from thedifference result calculated, determining a direction ofincrease/decrease from a control value of the control section to whichthe preceding input value belongs from the position information,calculating an input value variation width extending over controlsections from the difference result and the control width in the controlsection to which the preceding input value belongs, and calculating acontrol value for the input value this time from the input valuevariation width and the direction of increase/decrease.

According to anotner aspect of the present invention, a hysteresiscontrol apparatus comprises a reference value setting section that setsan arbitrary reference value which serves as a reference for deciding anexisting position of a control width in a control section of a pluralityof control sections which are input value operating variation widthshaving hysteresis control sections at both ends, a difference detectionsection that calculates a difference between an input value this timeand the arbitrary reference value in the control section to which apreceding input value belongs, a position information generation sectionthat generates position information indicating a positional relationshipbetween the input value this time and the arbitrary reference value inthe control section to which the preceding input value belongs from thedifference result calculated by the difference detection section, acontrol width selection section that selects the control width in thecontrol section to which the preceding input value belongs, an inputvalue variation width calculation section that calculates an input valuevariation width extending over control sections from the differenceresult calculated by the difference detection section and the controlwidth selected and output by the control width selection section, and acontrol value output section that calculates a control value for theinput value this time from the input value variation width and adirection of increase/decrease from a control value in the controlsection to which the preceding input value belongs obtained from theposition information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the invention will appearmore fully hereinafter from a consideration of the following descriptiontaken in connection with the accompanying drawing wherein one example isillustrated by way of example, in which;

FIG. 1 is a block diagram showing an example of the configuration of aconventional hysteresis control apparatus;

FIG. 2 is a time chart illustrating a control mode assumed whenhysteresis control is performed in a control system having a pluralityof control sections using the hysteresis control apparatus shown in FIG.1;

FIG. 3 is a block diagram showing an example of the configuration of acommunication apparatus using a hysteresis control method according toEmbodiment 1 of the present invention for transmit power control;

FIG. 4 is a flow chart illustrating a hysteresis control operationcarried out by the transmit power control section shown in FIG. 3;

FIG. 5 is a time chart specifically illustrating the hysteresis controlmethod shown in FIG. 4;

FIG. 6 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 2 of the present invention;

FIG. 7 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 3 of the present invention;

FIG. 8 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 4 of the present invention;and

FIG. 9 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 5 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now to the attached drawings, embodiments of the presentinvention will be explained in detail below.

Embodiment 1

FIG. 3 is a block diagram showing an example of the configuration of acommunication apparatus using a hysteresis control method according toEmbodiment 1 of the present invention for transmit power control.

The communication apparatus shown in FIG. 3 is provided with a wiredpropagation path interface section 101, a transmission baseband section102 connected to the output of the wired propagation path interfacesection 101, a radio section 103 connected to the output of thetransmission baseband section 102, an amplifier 104 that amplifies theoutput of the radio section 103 and a transmission antenna 105 thatradiates out the signal amplified by the amplifier 104 into the air.

The transmission baseband section 102 is provided with a codespreading/multiplexing section 106 that receives the output of the wiredpropagation path interface section 101, a transmit power control section107 that receives the output of the code spreading/multiplexing section106 and controls the radio section 103 and a band restriction filter 108that transmits the output of the transmit power control section 107 tothe radio section 103.

In the communication apparatus in the above described configuration,transmission data introduced by the wired propagation path interfacesection 101 from a wired propagation path is input to the transmissionbaseband section 102. The transmission data input to the transmissionbaseband section 102 is code-spread and code-multiplexed intotransmission data by the code spreading/multiplexing section 106,subjected to power control by the transmit power control section 107,subjected to band restriction by the band restriction filter 108 andoutput.

The transmission data output from the transmission baseband section 102is converted to an analog signal by the radio section 103, with transmitpower controlled according to an instruction from the transmit powercontrol section 107, amplified by the amplifier 104 and output from thetransmission antenna 105.

Here, the transmit power control section 107 determines to which controlsection the input value this time belongs from a difference between theinput value this time and an arbitrary reference value in theimmediately preceding (hereinafter referred to as “preceding”) inputvalue and determines the control value corresponding to the input valuethis time using the procedure shown in FIG. 4 and FIG. 5.

With reference to FIG. 4 and FIG. 5, the hysteresis control method usedby the transmit power control section 107 to control transmit power willbe explained. FIG. 4 is a flow chart which illustrates the hysteresiscontrol operation carried out by the transmit power control sectionshown in FIG. 3. FIG. 5 is a time chart specifically illustrating thehysteresis control method shown in FIG. 4.

In FIG. 4, in step ST201, an arbitrary reference value is set whichgives a reference for deciding the existing position of a control widthin a control section which corresponds to an input value operatingvariation width having hysteresis control sections at both ends. Thiswill be explained with reference to FIG. 5.

FIG. 5 shows four control sections a, b, c and d as control sectionswhich correspond to input value operating variation width havinghysteresis control sections at both ends. The control section b has acontrol value (output value) H, the control section c has a controlvalue (output value) I and the control section d has a control value(output value) J, but as shown in the control section c, an arbitraryreference value is set at a position where each control section isdivided into a control width 1 and control width 2. Here, A, B and Cshown in the control sections a, b and c in FIG. 5 are hysteresiscontrol sections.

In FIG. 5, each control section has an arbitrary width and the controlwidth 1 is different from the control width 2 (control width 1>controlwidth 2 in the example in the figure), but in another case where thecontrol sections have the same width, each control section may have thetwo equal control widths (see Embodiment 3 which will be describedlater) or a common arbitrary reference value may be set at the centerposition of all control sections so that the width of each controlsection is set to the control width (see Embodiment 4 which will bedescribed later).

In step ST202, a difference between the input value this time and anarbitrary reference value in the control section to which the precedinginput value belongs is calculated. In FIG. 5, the arbitrary referencevalue in the preceding input value is an arbitrary reference value ofthe control section c and FIG. 5 shows that the input value this time issubtracted from this arbitrary reference value (that is,difference=reference value−input value). However, though FIG. 5 shows animage in which the input value this time exists within the controlsection d, the “value of the input signal” is simply known in actualityand it is unknown to which control section the input value belongs.

In step ST203, position information indicating a positional relationshipbetween the input value this time and the arbitrary reference value inthe control section to which the preceding input value belongs isgenerated from the difference result obtained in step ST202. In theexample shown in FIG. 5, if the “reference value−input value” which isthe difference result is “positive”, it is detected that the input valuethis time is located on the side where control width 2 exists (on theside where the input value is smaller than the arbitrary reference valueof the control section c in the example shown in the figure) and if itis “negative”, it is detected that the input value this time is locatedon the side where control width 1 exists (on the side where the inputvalue is greater than the arbitrary reference value of the controlsection c in the example shown in the figure). Such position informationis generated in this step.

In step ST204, a direction of increase/decrease is determined from thecontrol value in the control section to which the preceding input valuebelongs from the position information generated in step ST203.

In step ST205, an input value variation width which extends over thecontrol sections is obtained from the difference result obtained in stepST202 and the control width in the control section to which thepreceding input value belongs and the control section to which inputvalue this time belongs is determined. Here, when the control sectionconsists of two control widths, the control width in the control sectionto which the preceding input value belongs is one of the control widthsdetermined by the position information. When the control sectionconsists of one control width, the control width is always that onecontrol width irrespective of the position information.

The input value variation width which extends over the control sectionscan be obtained using the following two methods:

(1) First, as the first method, it is possible to repeatedly subtractthe control width determined by, for example, position information fromthe first difference result and obtain an input value variation widthfrom the number of subtractions when the first subtraction result fallsbelow the control width (see Embodiments 2 to 4 which will be describedlater).

(2) Furthermore, as the second method, it is possible to divide thefirst difference result by the control width determined by, for example,the position information and use the division result as the input-valuevariation width (see Embodiment 5 which will be described later).

Here, the first difference result refers to a difference between anarbitrary reference value in the control section to which the precedinginput value belongs and the input value this time.

The case where the input value variation width which extends over thecontrol sections is obtained using the method in (1) will be explainedwith an example shown in FIG. 5. When the input value this time islocated on the side on which the control width 1 in the control sectionc exists, one subtraction results in the second differenceresult<control width 1, and therefore the control section to which theinput value this time belongs is determined to be the control section d.Furthermore, when the input value this time is located on the side onwhich the control width 2 in the control section c exists, the controlsection to which the input value this time belongs is determined as thecontrol section b or control section a depending on the number ofsubtractions. Here, the second difference result means the subtractionresult obtained by repeatedly subtracting a specified control width fromthe first difference result.

In step ST206, a control value (output value) corresponding to the inputvalue this time is obtained from the direction of increase/decrease fromthe control values in the control section to which the preceding inputvalue belongs obtained in step ST204 and the input value variation widthobtained in step ST205.

In the example shown in FIG. 5, when the preceding control section cmakes a transition to the control section d, a calculation in thedecreasing direction is applied to the control value I and the controlvalue J is obtained and when the preceding control section c makes atransition to the control section b, a calculation in the increasingdirection is applied to the control value I and the control value H isobtained.

In this way, according to the hysteresis control method of thisembodiment, in a control system including a plurality of controlsections which are input value operating variation widths havinghysteresis control sections at both ends, arbitrary reference valueswhich become references for deciding the existing positions of controlwidths in the control section are set, a difference between the inputvalue this time and the preceding input value is determined, thepositional relationship between the input value this time and arbitraryreference value of the preceding input value is detected from thedifference result, the input value variation width extending over thecontrol sections are detected from the difference result and the controlwidth in the preceding control section, a calculation is made on thecontrol value (output value) in the preceding input value using thedirection of increase/decrease from the control value in the precedinginput value obtained from the detected positional relationships andinput value variation width and the control value (output value) on theinput value this time is obtained, and therefore it is possible todecide to which control section the input value this time belongs by asingle comparison operation. Furthermore, the set value need not bechanged, either and it is thereby possible to simplify the apparatus forperforming the hysteresis control method of this embodiment.Furthermore, it is also possible to detect the input value variationwidth extending over the control sections simultaneously.

The apparatus for implementing the above described hysteresis controlmethod will be explained more specifically below.

Embodiments 2 to 4 show the case where the control width is subtractedfrom the difference result and the input value variation width iscalculated from the number of subtractions until the subtraction resultfalls below the control width as the method for calculating the inputvalue variation width extending over the control sections. That is, byrepeating subtractions of the control width from the difference resultuntil it falls below the control width, it is possible to calculate theinput value variation width from the number of subtractions.

Embodiment 2

Embodiment 2 will describe a case where when the input value operatingvariation width is an arbitrary width in a plurality of controlsections, respective arbitrary reference values are set at a positionwhere each control section is divided into a first control width andsecond control width.

FIG. 6 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 2 of the present invention.

The hysteresis control apparatus shown in FIG. 6 is provided with afirst difference detection section 401 that determines a differencebetween an input value this time and an arbitrary reference value in thecontrol section to which the preceding input value belongs, a positionconfirmation section 402 that detects position information indicating apositional relationship between the input value this time and thearbitrary reference value based on the difference result from the firstdifference detection section 401, a control section variationcalculation section 403 that detects how many control section variationshave taken place from the difference result at the first differencedetection section 401 and outputs the control section information, afirst control width selection section 404 that selects the control width(control width 1 or control width 2 shown in FIG. 5) based on thecontrol section information from the control section variationcalculation section 403 and position information from the positionconfirmation section 402 and outputs the control width to the firstdifference detection section 401, a first reference value settingsection 405 that sets an arbitrary reference value (see FIG. 5)determined in the control section based on the control sectioninformation from the control section variation calculation section 403and outputs the arbitrary reference value to the first differencedetection section 401 and a control section output section 406 thatdetermines and outputs the control value this time from the direction ofincrease/decrease from the preceding control value indicated by theposition information from the position confirmation section 402 andvariation width determined by the control section variation calculationsection 403.

The operation of the hysteresis control apparatus in the above describedconfiguration will be explained below.

Various input values are input to the first difference detection section401. Every time an input value is input, the first difference detectionsection 401 captures an arbitrary reference value in the control sectionto which the preceding input value output from the first reference valuesetting section 405 belongs, calculates a difference between thearbitrary reference value and input value this time (first differenceresult) (see FIG. 5) and outputs the difference to the positionconfirmation section 402.

When the position confirmation section 402 receives the first differenceresult from the first difference detection section 401, it obtainsposition information (see FIG. 5) indicating the positional relationshipbetween the arbitrary reference value in the control section to whichthe preceding input value belongs and input value this time from thefirst difference result and outputs the position information obtained tothe first control width selection section 404 and the control sectionoutput section 406.

Furthermore, after obtaining the first difference result, the firstdifference detection section 401 repeatedly subtracts the control widthoutput by the first control width selection section 404 from the firstdifference result and when this subtraction result (second differenceresult) falls below the control width, it outputs the number ofsubtractions and the second difference result to the control sectionvariation calculation section 403.

The control section variation calculation section 403 selects thecorresponding control section from the number of subtractions anddecides whether the second difference result is below the control widthin the selected control section or not. Then, when the decision resultshows that the second difference result is below the control width inthe selected control section, the control section variation calculationsection 403 gives the control section information indicating theselected control section to the first control width selection section404, first reference value setting section 405 and control sectionoutput section 406. On the other hand, when the decision result showsthat the second difference result is not below the control width in theselected control section, the control section variation calculationsection 403 gives the control section information indicating thepreceding control section to the first control width selection section404, first reference value setting section 405 and control sectionoutput section 406.

The first control width selection section 404 selects the control widthin the control section based on the control section information from thecontrol section variation calculation section 403 and positioninformation from the position confirmation section 402 and outputs theselected control width to the first difference detection section 401.The first difference detection section 401 uses the control width forthe next input value.

The first reference value setting section 405 receives the controlsection information from the control section variation calculationsection 403, sets an arbitrary reference value in the control sectionand outputs the set arbitrary reference value to the first differencedetection section 401. The first difference detection section 401 usesthe arbitrary reference value for the next input value.

The control section output section 406 determines the direction ofincrease/decrease from the control value in the control section to whichthe preceding input value belongs according to the position informationfrom the position confirmation section 402 and when the input valuevariation width from the control section variation calculation section403 exceeds the control section, it applies a calculation in thedirection of increase/decrease to the control value in the controlsection to which the preceding input value belongs, outputs thecalculation result as the control value in the control section to whichthe input value this time belongs and stores the calculation result asthe control value for the next input value.

Thus, when the input value operating variation width is an arbitrarywidth in a plurality of control sections, this embodiment can determinea difference between the input value this time and an arbitraryreference value in the control section to which the preceding inputvalue belongs, detect the input value variation width from the controlvalue in the control section to which the preceding input value belongsfrom the difference result and output the control value according to thedetected input value variation width. Therefore, when each controlsection is an arbitrary variation width, only one comparison operationis required in each hysteresis control section and it is possible toperform desired hysteresis control, capable of determining the controlvalue without the necessity to change the set value and also detect aninput value operation variation extending over the control sectionswhile performing hysteresis control.

Embodiment 3

Embodiment 3 will describe a case where when input value operatingvariation widths are equal across a plurality of control sections,respective arbitrary reference values are set at a position at whicheach control section is divided into two equal control widths.

FIG. 7 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 3 of the present invention. InFIG. 7, the components identical or equivalent to those in theconfiguration shown in FIG. 6 are assigned the same reference numerals.Here, mainly parts related to this Embodiment 3 will be explained.

The hysteresis control apparatus according to Embodiment 3 shown in FIG.7 is provided with a second control width selection section 501 insteadof the first control width selection section 404 in the configurationshown in FIG. 6 and a second reference value setting section 502 insteadof the first reference value setting section 405.

In FIG. 5, the control sections may have the same size or differentsizes, but the control width 1 has the size different from that of thecontrol width 2. On the contrary, the respective control sections inthis embodiment have the same size and the second reference valuesetting section 502 sets an arbitrary reference value at a position(central position) where the respective control sections have the twoidentical control widths.

Therefore, the second control width selection section 501 does not havetwo control widths to be selected for each control section but simplyhas two control widths which are commonly applicable to the respectivecontrol sections to be selected.

The operation of the hysteresis control apparatus in the above describedconfiguration will be explained below.

The second control width selection section 501 selects either a controlwidth on the side smaller or a control width on the side greater thanthe arbitrary reference value in the control section based on thecontrol section information from the control section variationcalculation section 403 and position information from the positionconfirmation section 402 and outputs the selected control width to thefirst difference detection section 401.

Thus, even when the two control widths in the respective controlsections are equal, it is possible to calculate a difference between theinput value this time and the arbitrary reference value in the controlsection to which the preceding input value belongs, detect the inputvalue variation width from the control value in the control section towhich the preceding input value belongs from the difference result andoutput the control value according to the detected input value variationwidth.

At this time, when two control widths in each control section are thesame, the second control width selection section 501 only needs to havetwo control widths; a control width on the side greater and a controlwidth on the side smaller than the arbitrary reference value, requiringonly a small number of control widths to be selected.

That is, as the control widths provided to be selected, it is onlynecessary to keep the control width on the side greater and the controlwidth on the side smaller than the arbitrary reference value common tothe respective control sections, and therefore it is possible to performcontrol with two values for when an input value is higher than thearbitrary reference value and when an input value is lower than thearbitrary reference value and thereby simplify the configuration.

Embodiment 4

Embodiment 4 will describe a case where an arbitrary reference value isset at a position where a plurality of control sections are divided intotwo equal parts when input value operating variation widths are equalacross a plurality of control sections.

FIG. 8 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 4 of the present invention. InFIG. 8, the components identical or equivalent to those in theconfiguration shown in FIG. 6 are assigned the same reference numerals.Here, mainly parts related to this Embodiment 4 will be explained.

The hysteresis control apparatus according to Embodiment 4 shown in FIG.8 is provided with a third control width selection section 601 insteadof the first control width selection section 404 in the configurationshown in FIG. 6 and a third reference value setting section 602 insteadof the first reference value setting section 405.

In FIG. 5, the control sections may have the same size or differentsizes, but the control width 1 has the size different from that of thecontrol width 2. On the contrary, the respective control sections inthis embodiment have the same size and the third reference value settingsection 602 sets an arbitrary reference value at a central position ofall the control sections.

Furthermore, the third control width selection section 601 outputscontrol widths which are fixed all the time independently of positionalrelationships detected by a position confirmation section 402. That is,all the control sections have the same size, and therefore the controlwidth here is the overall width of one control section.

The operation of the hysteresis control apparatus in the above describedconfiguration will be explained below.

The third control width selection section 601 outputs a control widthwhich is always constant up to the neighboring control sectionirrespective of the positional relationship detected by the positionconfirmation section 402 to a first difference detection section 401.

The first difference detection section 401 calculates a difference(first difference result) between an arbitrary reference value which isset in the center of all control sections by the third reference valuesetting section 602 and the input value this time, subtracts one controlwidth output by the third control width selection section 601 from thefirst difference result to obtain a second difference result and givesthe respective difference results to the control section variationcalculation section 403.

Thus, according to this Embodiment 4, even when control sections havethe same size and are treated as one fixed control width and anarbitrary reference value is set as a central position value for allcontrol sections, it is possible to calculate a difference between aninput value this time and an arbitrary reference value in the controlsection to which the preceding input value belongs, detect an inputvalue variation width from the control value in the control section towhich the preceding input value belongs from the difference result andoutput the control value according to the detected input value variationwidth.

At this time, if the respective control sections have the same size andare treated as one fixed control width and when an arbitrary referencevalue is set as the central value of all the control sections, only onearbitrary reference value needs to be set by the third reference valuesetting section 602. Furthermore, the third control width selectionsection 601 only needs to have one control width to be selected.

Thus, only one arbitrary reference value needs to be set and only onecontrol width needs to be prepared as the one to be selected, andtherefore it is possible to further simplify the configuration.

Embodiment 5

Embodiment 5 will describe a case where a result of dividing adifference result by a control width is used as an input value variationwidth as the method for calculating an input value variation widthextending over control sections.

FIG. 9 is a block diagram showing the configuration of a hysteresiscontrol apparatus according to Embodiment 5 of the present invention. InFIG. 9, the components identical or equivalent to those in theconfiguration shown in FIG. 7 are assigned the same reference numerals.Here, mainly parts related to this Embodiment 5 will be explained.

The hysteresis control apparatus according to Embodiment 5 shown in FIG.9 is provided with a second difference detection section 701 instead ofthe first difference detection section 401 in the configuration shown inFIG. 7. Furthermore, the control section variation calculation section403 is omitted and a control section output section 702 is providedinstead of the control section output section 406.

The second difference detection section 701 divides the differencebetween an arbitrary reference value set by a second reference valuesetting section 502 and an input value this time by a control widthoutput by a second control width selection section 501.

The control section output section 702 receives the output of the seconddifference detection section 701 and the output of the positionconfirmation section 402. The second reference value setting section 502obtains control section information from the control section outputsection 406.

The operation of the hysteresis control apparatus in the above describedconfiguration will be explained below.

The second difference detection section 701 calculates a difference(first difference result) between an arbitrary reference value set bythe second reference value setting section 502 and an input value thistime and divides the first difference result by the control width outputby the second control width selection section 501 to calculate a seconddifference result and give the second difference result to the controlsection output section 406.

The control section output section 702 determines a direction ofincrease/decrease from a control value in the control section to whichthe preceding input value belongs from the position information from theposition confirmation section 402, regards the second difference result(division result) at the second difference detection section 701 as aninput value variation width, outputs control section informationobtained from the input value variation width to the second referencevalue setting section 502, applies a calculation in the direction ofincrease/decrease to the control value in the control section to whichthe preceding input value belongs, outputs the calculation result as acontrol value this time and stores the calculation result as the nextinput value control value.

Thus, when two control widths in each control section are the same, thisembodiment can calculate a difference of an input value this time andpreceding input value from the arbitrary reference value, divide thedifference result by either one control width to detect an input valuevariation width from the control value in the control section to whichthe preceding input value belongs and output the control value accordingto the detected input value variation width.

In Embodiments 2 to 4, the difference detection section calculates aninput value variation width, but the present invention may also beadapted so that the control section variation calculation sectiondirectly calculates the input value variation width. The method ofcalculating the input value variation width shown in Embodiment 5through a division operation may also be used in Embodiments 2 to 4instead of a subtraction operation.

As explained above, when there is a plurality of control sections whichare input value operating variation widths having hysteresis controlsections at both ends, the present invention needs only one comparisonoperation in each hysteresis control section, can calculate controlvalues without any need to change set values and detect input valuevariation widths extending over control sections while carrying outhysteresis control.

The present invention is not limited to the above described embodiments,and various variations and modifications may be possible withoutdeparting from the scope of the present invention.

This application is based on the Japanese Patent Application No.2003-088162 filed on Mar. 27, 2003, entire content of which is expresslyincorporated by reference herein.

1. A hysteresis control method in a control system having a plurality ofcontrol sections which are input value operating variation widths havinghysteresis control sections at both ends, comprising: setting anarbitrary reference value which serves as a reference for deciding anexisting position of a control width in a control section; calculating adifference between an input value this time and the arbitrary referencevalue in the control section to which a preceding input value belongs;generating position information indicating a positional relationshipbetween the input value this time and the arbitrary reference value inthe control section to which the preceding input value belongs from adifference result calculated; determining a direction ofincrease/decrease from a control value of the control section to whichthe preceding input value belongs from the position information;calculating an input value variation width extending over the controlsections from the difference result and the control width in the controlsection to which the preceding input value belongs; and calculating thecontrol value for the input value this time from the input valuevariation width and the direction of increase/decrease.
 2. A hysteresiscontrol apparatus comprising: a reference value setting section thatsets an arbitrary reference value which serves as a reference fordeciding an existing position of a control width in a control section ofa plurality of control sections which are input value operatingvariation widths having hysteresis control sections at both ends; adifference detection section that calculates a difference between aninput value this time and the arbitrary reference value in the controlsection to which a preceding input value belongs; a position informationgeneration section that generates position information indicating apositional relationship between the input value this time and thearbitrary reference value in the control section to which the precedinginput value belongs from a difference result calculated by saiddifference detection section; a control width selection section thatselects the control width in the control section to which the precedinginput value belongs; an input value variation width calculation sectionthat calculates an input value variation width extending over thecontrol sections from the difference result calculated by saiddifference detection section and a control width selected and output bysaid control width selection section; and a control value output sectionthat calculates a control value for the input value this time from theinput value variation width and a direction of increase/decrease fromthe control value in the control section to which the preceding inputvalue belongs obtained from the position information.
 3. The hysteresiscontrol apparatus according to claim 2, wherein when the input valueoperating variation width is an arbitrary width in a plurality ofcontrol sections, said reference value setting section sets thearbitrary reference value at a position at which the control sectionspecified by control section information is divided into a first controlwidth and a second control width as an arbitrary reference value in thecontrol section to which the preceding input value belongs, said controlwidth selection section outputs the control width which is determined bythe position information out of the first control width and the secondcontrol width specified by the control section information as thecontrol width in the control section to which the preceding input valuebelongs, and said input value variation width calculation sectionoutputs the control section information when the input value variationwidth is calculated.
 4. The hysteresis control apparatus according toclaim 3, wherein said input value variation width calculation sectionsubtracts the control width in the control section to which thepreceding input value belongs from the difference result calculated bysaid difference detection section and calculates the input valuevariation width from the number of subtractions until the subtractionresult falls below the control width.
 5. The hysteresis controlapparatus according to claim 3, wherein said input value variation widthcalculation section regards the result of dividing the difference resultcalculated by said difference detection section by the control width inthe control section to which the preceding input value belongs as theinput value variation width.
 6. The hysteresis control apparatusaccording to claim 2, wherein when the input value operating variationwidths are the same across a plurality of control sections, saidreference value setting section sets the arbitrary reference value at aposition at which control sections are divided into equal control widthsas an arbitrary reference value in the control section to which thepreceding input value belongs, and the control width selection sectionoutputs the control width which is determined by the positioninformation out of the two equal control widths in the control sectionas a control width in the control section to which the preceding inputvalue belongs.
 7. The hysteresis control apparatus according to claim 6,wherein said input value variation width calculation section subtractsthe control width in the control section to which the preceding inputvalue belongs from the difference result calculated by said differencedetection section and calculates the input value variation width fromthe number of subtractions until the subtraction result falls below thecontrol width.
 8. The hysteresis control apparatus according to claim 6,wherein said input value variation width calculation section regards theresult of dividing the difference result calculated by said differencedetection section by the control width in the control section to whichthe preceding input value belongs as the input value variation width. 9.The hysteresis control apparatus according to claim 2, wherein when theinput value operating variation widths are the same across a pluralityof control sections, said reference value setting section sets thearbitrary reference value at a position at which all of the plurality ofcontrol sections are divided into two equal parts as an arbitraryreference value in the control section to which the preceding inputvalue belongs, and the control width selection section outputs onecontrol width indicating the width of the control section as the controlwidth in the control section to which the preceding input value belongs.10. The hysteresis control apparatus according to claim 9, wherein saidinput value variation width calculation section subtracts the controlwidth in the control section to which the preceding input value belongsfrom the difference result calculated by said difference detectionsection and calculates the input value variation width from the numberof subtractions until the subtraction result falls below the controlwidth.
 11. The hysteresis control apparatus according to claim 9,wherein said input value variation width calculation section regards theresult of dividing the difference result calculated by said differencedetection section by the control width in the control section to whichthe preceding input value belongs as the input value variation width.12. The hysteresis control apparatus according to claim 2, wherein saidinput value variation width calculation section subtracts the controlwidth in the control section to which the preceding input value belongsfrom the difference result calculated by said difference detectionsection and calculates the input value variation width from the numberof subtractions until the subtraction result falls below the controlwidth.
 13. The hysteresis control apparatus according to claim 2,wherein said input value variation width calculation section regards theresult of dividing the difference result calculated by said differencedetection section by the control width in the control section to whichthe preceding input value belongs as the input value variation width.14. A hysteresis control method, comprising: calculating a differencebetween a first input value and an arbitrary reference value, thearbitrary reference value corresponding to a first range of inputvalues, within which a preceding input value, which precedes the firstinput value, falls; generating position information based on whether thefirst input value is greater than or less than the arbitrary referencevalue; determining an increase/decrease direction based on the positioninformation; calculating a second range of input values based on thecalculated difference between the first input value and the arbitraryreference value, and based on a control width corresponding to the firstrange of input values; and calculating a control value for the firstinput value based on the calculated second range of input values and theincrease/decrease direction.
 15. A hysteresis control method accordingto claim 14, further comprising determining the control width based onthe position information.
 16. A hysteresis control method according toclaim 14, further comprising subtracting the control width from thecalculated difference between the first input value and the arbitraryreference value one or more times until a result of the one or moresubtractions is less than the control width, wherein the second range ofinput values is calculated based on the number of subtractions.
 17. Ahysteresis control method according to claim 14, wherein the secondrange of input values is calculated by dividing the calculateddifference between the first input value and the arbitrary reference bythe control width.